Fix test_import_contacts_from_sim.py

The test is failing in Jenkins because the tap is not being performed. I added a wait for the settings button to appear and it fixed the problem.

Here is the adhoc test results for the tests:
http://qa-selenium.mv.mozilla.com:8080/view/B2G/job/b2g.unagi.mozril.gaia.v1-train.ui.run_adhoc_tests/15/console

v1-train -> Merge.
master -> Test & merge if needed.